This book was for me the most informative and interesting physics popularization I have ever read, but then I was a physics major in the 1970s before moving on to an unrelated career. While containing only a little math as such, there is a great deal of jargon filled discussion that I was comfortable with because of my background that might cause readers who haven’t had as much exposure to physics to get a little bit lost. I encourage potential readers who would like having the general physics background to be completely comfortable with books like this one to watch Leonard Susskind’s excellent half-dozen different ten-lecture series on different subjects within physics, which can be found on YouTube and at theoreticalminimum.com, although these require having some comfort with basic calculus. If you don’t want to deal with the math, then watch as many relevant videos as you are willing to on the excellent PBS Spacetime YouTube channel in order to get more comfort with as much physics and cosmology as you like at a non-mathematical level.
I graduated just before Alan Guth came up with cosmic inflation, and never really focused on cosmology. I had heard the theory was meant to solve the horizon and flatness problems (discussed in this book) but always felt that these problems could be solved in other as yet unknown ways without the need for a theory that seems so ad hoc in terms of positing mechanisms for no underlying reasons other than to produce the desired effect. And Will Kinney says as much in the last chapter of his book: “Geometric flatness and homogeneity could reasonably be taken as boundary conditions, set by some as yet unknown symmetry.”
But he then continues “Cosmic perturbations are a different matter.” The real surprise and new news for me (and Kinney goes through the ins and outs of this in detail, citing the actual papers of the relevant physicists) is that the tiny angular fluctuations in the strength and polarization of the cosmic microwave background radiation, successfully measured by satellites launched for that purpose in recent decades, can be explained by no other known or hypothesized process than inflation, clinching the case for this strange theory. So it looks like the cosmos really is crazier than I had thought, and than I had hoped.
Beyond the strong case made for the reality of cosmic inflation itself, the book has two other important subtexts. One is that, particularly when combined with string theory (if string theory is in fact true) the laws of physics in effect in what is for us the whole observable universe are anthropically selected from a very large ensemble of different sets of laws. So-called eternal inflation provides a mechanism for generating a potentially infinite collection of isolated universes that vary in their physical laws according to the vast array of possible different string theory compactifications. Kinney makes it clear that he is very uncomfortable with and unsatisfied by anthropic reasoning, although I think that in an appropriate set-up, anthropic reasoning is tautologically true.
The other subtext with which I sadly agree is that cosmology (and I think also fundamental physics as a whole) is probably reaching the limits of what we can know. I believe the limitation on how much further we can explore energies in accelerator experiments is well-known and clear. But Kinney makes the point that the evidence we have already collected, which appears to clinch the case for inflation, might be at the limit of what we can possibly collect because of the way a period of cosmic inflation censors and hides the physics that came earlier. So neither data from the lab nor observations of the universe may give us much more insight into fundamental physics than what we already have. I’ll risk giving it away, but at the end of the book he writes “Our understanding may have fundamentally inescapable limits, and we may ultimately have to learn to live in the presence of the nameless as we seek to comprehend the ultimate origin of the cosmos. There may be no other way.”
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A phenomenal introduction to the making of the modern Multiverse
In An Infinity of Worlds, Kinney picks up where Guth’s The Inflationary Universe left off 25 years ago. A vibrant refresher on the subject, thoroughly documenting the latest observations and challenges to the theory of inflation. Kinney’s shimmering prose demystifies this most-inscrutable cosmic epoch and illuminates the way for future generations of researchers to explore its many remaining mysteries.Beautifully bound and printed with delightful images, you’ll treasure this time for all time!Brian Keating Chancellor’s Distinguished Professor of Physics at UC San Diego,
Spitzenrezensionen aus anderen Ländern
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Lindsay ForbesBewertet in Großbritannien am 26. Juni 2022
An in depth and honest review of Inflation.
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RobBewertet in Australien am 2. Oktober 2023
Deep and insightful journey into modern cosmology
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Jon Ellis.Bewertet in Großbritannien am 6. Oktober 2023
Understanding for the arts graduate.
